MIT researchers developed this "Soft Cube Capable of Controllable Continuous Jumping." From IEEE Spectrum:
Inside of the robot there are two motorized rotors, each connected to one end of four flattened loops of spring steel. Activating the rotors causes the spring steel loops that I'm just going to go ahead and call tongues to get pulled through rectangular openings (mouths) into a round cavity inside the body of the robot, compressing them. As the rotors continue to turn, eventually the compressed tongues get pulled all the way around back to the mouths, at which point they spring out, releasing that elastic energy all at once and causing the robot to jump.
"With some light-weight payloads, such as miniature cameras, the robot can be used for exploration tasks," write the researchers. "Moreover, a wireless sensor network can be automatically deployed and reconfigured for outdoor surveillance by using a group of our jumping robots."
Next, they hope to increase the robots' power so the cubes can jump higher and cover more ground.
"MIT's Cube Robot Uses Springy Metal Tongues to Jump" (IEEE Spectrum)